Few thoughts to animate the round table

1. Few thoughts to animate the round table (thanks to the contributors)

2. 2nd MPI@LHC Progress with respect to the 1st MPI w/s • First LHC papers, further papers from Tevatron, RHIC, etc. • Tevatron: Emphasis on high lumi DPS measurements • LHC: Traditional MB/UE/Diffr phenomenology + some “surprises”  long range correlations in high multiplicity events HI inspired interpretations: QG? Angular conservation in MPI? • Progress in MC generators • Sherpa, Herwig++, Pythia8, EPOS, … • Progress in MC tuning • Professor and manual tunes using the fresh LHC data • MPI TH progress • 2009 and 2010 publications with “MPI” keyword: [Treleani, Strikman, Maina, Diehl, Lipari, Lusignolo, Magri, Skachkov, Abramovsky, Nagy, etc. etc. etc.]

3. MPI w/s Ideas for improvements • While aiming at improving things we should not discard the good features • Bringing together heterogeneous communities (pp/central, pp/FWD, HI, EXP, TH, Pheno) focusing on research lines dealing with MPI • Plenary meetings • Format • General feeling that there should be more time allowed for discussion • Introductory talks may be useful, not only for students • Talks still tend to start “in medias res” (adequate for specialists) • … • Content • This is not the MBUE w/g, of course there are interplays but in this context we should rather try to focus on MPI concepts • MC models are certainly essential tools. Tuning them is important for any physics programme. • Having alternative tunes accounting for TH uncertainties is also important • Pursuing universality may also be instructive but… • In our context we want to go well beyond these MC-related goals!

4. List of requirements and Open issues Initiatives to strengthen the contacts between the different communities: terminology, benchmarks • Quote seff in MC tunes and in measurements (where applicable) • seff from geometry • seff from interaction counting (in particular from ratio of momenta) • … • pT cut offs regulating divergences and the amount of MPIs in MC models are often key MC parameters, their energy dependence “reminds” important observables related to diffraction: Pomeron intercept etc. Would it be possible to make an effort to give a deeper physical meaning to them? • Selecting “hard” objects to measure seff is not sufficient to describe essential observables which depend on “soft” additional interactions: UE activity, isolations, Jet pedestals etc. • Successful MC models/tunes favor color connections between interactions • Quite few criticisms to this approach from the TH (not MC) community • Are there alternative approaches? Dynamical description of interacting hadrons? • …  Let’s complete at least the list of requirements early 2011 and let’s try to implement the recommendations in the proceedings.

5. Proceedings of the 2nd MPI@LHC w/sand 3rd MPI@LHC w/s • Proceedings (deadline April 30th 2011) • Paper version? DESY-PROC • Electronic version? • Candidatures for the 3rd MPI@LHC w/s • Desy (Zoltan Nagy) • … • Late Autumn 2011 • Adequate for 2011 LHC high lumi run • An early workshop may help to avoid proliferation of similar initiatives re-directing the resources in our context • Easy to predict an increasing interest in MPI bkg to seaarches • Late Spring 2012 • Back-up option